Color deformographic storage target

ABSTRACT

A target assembly for a storage/display deformographic tube comprising a Fabry-Perot type interference filter deposited on a dielectric target material. The filter comprises a deformographic film sandwiched between two mirrors, the inner dielectric mirror comprised of a quarter wavelength stack of alternating layers of materials with greatly differing indexes of refraction and the outer conducting mirror comprising a thin layer of appropriate metal such as silver. The deformographic film should be deposited in a layer which is an integral number of one-half wavelengths.

United Sta Dalton et al.

[ Aug. 26, 1975 1 COLOR DEFORMOGRAPHIC STORAGE TARGET [75] Inventors:John J. Dalton, Rhinebeck; Neil M.

Poley, Kingston, both of NY.

International Business Machines Corporation, Armonk, NY.

[22] Filed: July 16, 1973 [21] Appl. No.: 379,672

[73] Assignee:

51 im. c1.%.n01,1 31/48; HOlJ 29/12; @0113 9/02; G02F 1/21 [58] Field OfSearch 178/54 BD, 7.5 D, 7.88; 313/89, 91, 461, 465, 394, 397, 398;

350/161 DM, 161 so; 356/112; 358/62 [56] References Cited UNITED STATESPATENTS 3,385,927 5/1968 Hamann 178/75 D 3,498,694 3/1970 Hamann 356/1123500237 3/1970 Myers et a1; 356/112 3,699,242 10/1972 Price 178/54 BDUNIFORM CHARGE 127 OTHER PUBLICATIONS IBM Technical Disclosure Bulletin,Vol. 6, No. 7, Dec. 1963, pp. 55-56, Light Modulator A. H. Nethercot,Jr.

Primary ExaminerRobert L. Griffin Assistant ExaminerGeorge G. StellarAttorney, Agent, or Firm-Charles E. Rohrer [57] ABSTRACT A targetassembly for a storage/display deformographic tube comprising aFabry-Perot type interference filter deposited on a dielectric targetmaterial. The filter comprises a deformographic film sandwiched betweentwo mirrors, the inner dielectric mirror comprised of a quarterwavelength stack of alternating layers of materials with greatlydiffering indexes of refraction and the outer conducting mirrorcomprising a thin layer of appropriate metal such as silver. Thedeformographic film should be deposited in a layer which is an integralnumber of one-half wavelengths.

2 Claims, 2 Drawing Figures ail/ (4 1 COLOR DEFORMOGRAPHIC STORAGETARGET This invention relates to storage/display tubes used for thevisible presentation of information transduced from electricalinformation bearing signals and more particularly to a deformographictarget assembly of the Fabry-Perot type capable of providing a colorvisual display.

CROSS REFERENCE TO RELATED PATENTS U.S. Pat. No. 3,109,062 to Clauer andKuehler issued Oct. 29, 1963.

U.S. Pat. No. 3,445,707 to Hershoff and Gilvey issued May 20, 1969.

U.S. Pat. No. 3,626,084 to Wohl, Hawn and Medley issued Dec. 7, 1971.

U.S. Pat. No. 3,676,588 to Kozol and Wohl issued July 11, 1972.

All of these patents relate to storage/display tubes and improvementstherein and all are assigned to the assignee of the present invention.U.S. Pat. No. 3,626,084 is specifically incorporated herein byreference.

BACKGROUND OF THE INVENTION The conventional method of providing astatic visual display of information transmitted in the form ofelectrical signals is by meansof a cathode ray tube having a phosphorcoated face on which an electron beam impinges to produce a visibledisplay. The beam carried information by undergoing modulation of eitherthe intensity of the deflection of the electron beam. However, the useof phosphors for displays of the type contemplated herein, that is,storage as well as projection of the display, is not completelysatisfactory.

As a consequence, tubes have been developed and are described in theabove referenced patents wherein electron beams generated by electronguns of the type used in cathode ray tubes are directed to a dielectrictarget rather than a phosphor target. Electron depostion on thedielectric target provides an electrostatic charge pattern correspondingto the information which modulates the electron beam. That electrostaticcharge pattern is reproduced on the opposite side of the target in aspecial material which deforms according to the quantity ofelectrostatic charge deposited on the dielectric surface. The deformedmaterial may then be viewed through reflective or transmissive schlierenoptics and visual perception may be maintained satisfactorily for aperiod of hours after the electron beam generating gun is turned off.

All of these prior art deformographic tubes have provided black andwhite visual displays and have used schlieren optics. Consequently, itis the general object of this invention to provide a special targetassembly which is capable of providing a color visual display and whichdoes away with schlieren optics in black and white or color mode. Otherobjects and advantages of the invention will become apparent through thefollowing description.

SUMMARY OF THE INVENTION This invention provides a target assembly basedupon Fabry-Perot interference transmission filter techniques. The targetassembly comprises a target dielectric material one surface of which isdisposed to receive impinging electrons from an information bearingelectron beam. The opposite surface of the dielectric material is coatedwith a dielectric mirror which, in turn, is coated with a deformographicmaterial which is coated with a second mirror. The two mirrors sandwichthe deformographic material in a structure that provides a Fabry-Perottype of interference transmission so that a light beam directed to theassembly may be broken into its component colors. The result is thecapability of providing a background color for projection onto a screenand a second color delineating the deformities in the deformographicmaterial produced in accordance with the information bearing electronbeam.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partlybroken away, illustrating a deformographic storage display tube.

FIG. 2 is a cross-sectional partial view of the target assembly of thepresent invention used in the display system shown in FIG. 1.

DETAILED DESCRIPTION OF AN EMBODIMENT FIG. 1 illustrates a generalarrangement of a deformographic storage display tube. The tube includesan evacuated envelope 10 of any suitable shape such as that of aconventional cathode ray tube having an electron gun and focusing systemat one end and an enlarged transparent faceplate 12 at the other end.Individual write and erase guns are shown in separate necks extendingfrom the envelope 10. The write gun 14 includes a cathode l6 and acontrol grid 18 to which signals are applied to modulate the electronbeam inten sity in conventional fashion. The modulating input signalsmay be derived from any suitable source such as from video informationsignal circuits 20. The modulated electron beam is scanned across thesurface of dielectric target 22 by deflection means such as a deflectionyoke 24 disposed around the neck of the envelope l0 and controlled bysweep voltage generator 26. Although a video-type scanning system isshown, selective scanning or other displays may alternatively begenerated by digital-type circuits, by character beam-type tubes or byany other circuits appropriate for a particular application.

An erase gun 28 operated by erase control circuits 30 is utilized forerasure of the electrostatic charge distribution pattern on the writingside of the target 22. Erase gun 28 may be mounted in a separate neck ofthe envelope 10 and directs a dispersed high intensity beam onto thetarget surface. Details of the beam focusing and accelerating system arenot shown since they may assume any of a number of conventional forms.

The outer periphery of the target 22 is mounted to the inner wall of theenvelope 10 in appropriate sealed fashion, not shown in detail, todefine two separate and independent chambers 32 and 34 within theenvelope 10. The sealed chamber 32 on the one side of the dielectrictarget 22 is called the electron beam chamber because it contains thewrite gun l4 and the erase gun 28 and associated components. The sealedchamber 34 on the other side of the dielectric target 22 from thechamber 32 extends between the target and the tube faceplate 12 and maybe termed a deformographic film chamber since it contains adeformographic filter 36. Filter 36 will be described hereinafter indetail with respect to FIG. 2. It should be noted that two chamberconstruction is necessary only because of possible contamination ofcathods by gases given off by presently known suitable deformographicmaterials.

While reflective optics may be used, if desired, the system illustratedin FIG. 1 is a type of transmissive optical system. Light from a source60, which in this instance comprises a projection lamp, is focused alongan optical axis 62 by a condenser comprising a pair of lenses 64. Thefocused light passes through the tube faceplate 12 to the deformographicfilter 36 where it is refracted and diffracted by the deformationstherein. Light passing through the filter 36., the target 22, and anoptically clear window 68 comprising a flat surface or lens element inthe envelope reaches a projection lens 70 for projecting onto screen 74.It is obvious that the tube faceplate 12 must also be of optically clearmaterial and is a part of the lens system.

A normal Fabry-Perot interferometer is composed of two optical flats oretalons coated with semitransparent metals or dielectric films where thespacing between then is varied to produce interference fringes. Bysemi-transparent metal is meant a metal of controlled thickness so as toobtain satisfactory transparency. Reference may be made to the book ThinFilm Optical Filters by H. A. Macleod, published by the AmericanElsevier Publishing Company, lnc., New York, 1969 for explanatoryinformation concerning the theory of Fabry-Perot filters. Essentially,the Fabry- Perot interferometer is used for the examination of thestructure of spectral lines. Light is passed from a source through theinterferometer producing fringe patterns which give very preceise wavelengths varying as a function of the physical parameters of the filter.FIG. 2 shows, in cross section, the target assembly according to thepresent invention in which a Fabry-Perot interferometer is incorporatedby sandwiching deformographic material 124 between mirrors 123 and 125.For purposes of illustration, a point charge 126 and a uniform charge127 are shown as being deposited on the surface of the dielectric target122. These charges result in the deformations 128 and 129 shown in thedeformographic material 124. Since the outer mirror 125 is coated on thesurface of the deformographic material, these deformations are alsoincluded in mirror 125. Additionally, mirror 125 acts as a conductiveground plane for establishing a reference potential plane substantiallycoextensive with target 22. Reference may be made to U.S. Pat. No.3,676,588, mentioned above, for a more thorough explanation of the typeof ground plane provided herein.

In designing a filter 36 such as shown in FIG. 2, the deformographicmaterial 124 should be coated to a thickness which is an integralone-half wavelength of the frequency of light for which the filter isdesigned. The dielectric mirror 123 which should be semitransparent in atransmissive optical system, should be comprised of alternating layersof materials with a much different index of refraction. It might, forexample, be produced from alternating layers of zinc-sulfide andcryolite. It is necessary to use an odd number of layers and each layershould be optically a quarter wavelength thick. The semi-transparentconductive mirror 125 deposited over the deformographic material must bethin enough not to prevent the deformations from taking place in thedeformographic material but must be thick enough to provide thereflectivity necessary for the operation of the filter. Silver with athickness of N10 to 200 angstroms may provide suitable results.

in operation, the basic color for which the filter is designed might,for example, be blue. With such a target incorporated into the tubeshown in FIG. 1, the color blue would be projected upon the screen 74.The information written upon that backround might be red due to thedeformations 128 and 128 shown in FIG. 2. In order to gain the necessarycolor difference from the background color, all that is necessary is toadjust the intensity modulation on the electron gun when theelectrostatic charge is deposited on the dielectric target 122.

Thus, there has been described a filtering target assembly for use in adeformographic storage display tube which has color capability.importantly, it should be noted when a filter of this type is used,schlieren optics are not required, thus substantially reducing the costand complexity of this display system over the display systems shown inthe referenced patents. Other advantages include the fact that complexelectronics are not required to produce the color; write gum intensitymodulation is the essential difference from conventional black and whitedisplay systems. Also, if this tube is used in black and white mode, ithas been observed that contrast is enhanced because the two reflectingsurfaces of the filter result in more light out than is obtained throughthe prior art tubes with their complicated schlieren optics.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand de tails may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

1. In a deformographic storage/display tube wherein a modulated electronbeam deposits information on a target assembly and wherein light ispassed through or reflected from said target assembly to project saidinformation for visual display, a target assembly comprismg a dielectrictarget for receiving electrons from said electron beam and providing asurface for electrostatic charge build-up in accordance with beammodulation, said dielectric target retaining said charge build-up aftersaid beam is removed,

a dielectric mirror comprising optically a quarter wavelength stack ofan odd number of alternating layers of material said dielectric mirrordeposited on a second surface of said target opposite to the targetsurface upon which an electrostatic charge is built-up, deformographicmaterial deposited on the surface of said dielectric mirror to athickness which is an even number of half wavelengths,

a semi-transparent mirror and ground plan deposited on the surface ofsaid deformographic material to a thickness sufficient to providereflectivity for optical interference purposes and sufficiently thin toprovide an acceptably low level of hindrance to the deformation of thedeformographic material,

so that when a light beam is transmitted through or reflected from saidtarget, the deformographic material sandwiched between the two mirrorsacts as a type of Fabry-Perot interference filter to provide a basecolor for projection and a different color for the light projectedthrough the deformed areas of the deformographic material.

2. The target assembly of claim 1 wherein said alternating layers ofmaterial are zinc sulfide and cryolite and where said semi-transparentmirror and ground plane is comprised of silver to 200 angstroms thick.-4 i =l

1. In a deformographic storage/display tube wherein a modulated electronbeam deposits information on a target assembly and wherein light ispassed through or reflected from said target assembly to project saidinformation for visual display, a target assembly comprising adielectric target for receiving electrons from said electron beam andproviding a surface for electrostatic charge build-up in accordance withbeam modulation, said dielectric target retaining said charge build-upafter said beam is removed, a dielectric mirror comprising optically aquarter wavelength stack of an odd number of alternating layers ofmaterial said dielectric mirror deposited on a second surface of saidtarget opposite to the target surface upon which an electrostatic chargeis built-up, a deformographic material deposited on the surface of saiddielectric mirror to a thickness which is an even number of halfwavelengths, a semi-transparent mirror and ground plan deposited on thesurface of said deformographic material to a thickness sufficient toprovide reflectivity for optical interference purposes and sufficientlythin to provide an acceptably low level of hindrance to the deformationof the deformographic material, so that when a light beam is transmittedthrough or reflected from said target, the deformographic materialsandwiched between the two mirrors acts as a type of Fabry-Perotinterference filter to provide a base color for projection and adifferent color for the light projected through the deformed areas ofthe deformographic material.
 2. The target assembly of claim 1 whereinsaid alternating layers of material are zinc sulfide and cryolite andwhere said semi-transparent mirror and ground plane is comprised ofsilver 100 to 200 angstroms thick.